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Bio 101 - Lecture 8

Bio 101 - Lecture 8 - What's a plant What's the evolution p...

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Unformatted text preview: 1/28/2008 What's a plant? What's the evolution p y of the plant body form? Multicellular eukaryote Autotrophic (self-feeding) (self produces sugars via photosynthesis mineral nutrients and water f l d from environment Sexual and asexual reproduction Classification by: life cycle reproductive mode Life under water It's wet Mineral nutrients are all around you Gravity is no problem Easy trip for sex cells Kids leave home: go for a swim Life on land It's sometimes dry Gravity is a problem Water and nutrients in the ground CO2 in the air Sex without water? Kids leave home: Hitchin' a ride Blowing in the wind Mycorhizzal association Mycorhizzal association myco=fungus rhizo=root Helps plant absorb water and nutrients Receives sugars from plant Mycorhizzal association myco=fungus rhizo=root Helps plant absorb water and nutrients 1 1/28/2008 Highlights of plant evolution Moist Drier Strategies for surviving on land The Bryophyte Strategy (bryophytes are mosses and liverworts) Drying out? - Tolerate it! Gravity? - Stay small and even flat Getting nutrients? No vascular system Absorb from rainfall Sex without water? - Wait for rain Kids leave home: Explosive! or passive Stem of a giant lycophyte (Lepidodendron), which could grow 40 meters (131 feet) tall Stem of a giant horsetail (Calamites), which was almost 20 meters (66 feet) tall Seed fern (Medullosa); its seeds were about the size of walnuts Explosion of spore capsule of moss plant A Moss Plant 2 1/28/2008 Strategies for surviving on land Vascular Plant Strategy Ferns, trees, shrubs, and other flowering plants Drying out? - Develop cuticle f D i t? D l ti l for waterwater-proofing Liverwort from the Hocking Hills Cross section of a leaf cuticle Strategies for surviving on land Vascular Plant Strategy Getting nutrients? Roots for water and soil nutrients (e.g., N, P, K) Leaves for light and CO2 Transport from leaves to roots Specialized vascular tissues: Xylem distributes water and minerals Phloem distributes sugars from photosynthesis epidermis Gravity? G it ? Lignin sugar polymer in cell walls (wood) stoma Sex without swimming and kids leave home? Get animals and wind to help Flowers with adaptations for insects to transfer sex cells (pollen)... Flowers with adaptations for wind to transfer sex cells ...also birds and bats Hemp Grasses 3 1/28/2008 A quick survey of vascular plants Seedless vascular plants (produce spores) Whisk ferns (psilopsids) Resemble the very earliest land plants Photosynthetic cells in stems Club mosses (lycopods) Ferns Princess Pine or Ground Cedar: (club moss) Psilotum (whisk fern) Typical fern leaves (frond) with spore-producing sites Spores: Can develop into new fern without fusing to form a zygote (cells are haploid, n) Autotrophic no food supply (unlike seeds) Tough outer coats to resist harsh environments A quick survey of vascular plants Gymnosperms Conifers (cone-bearers) (coneAbout Ab t 700 species i Provide lumber and paper pulp Cycads resemble palm trees Gingko Gnetophytes e.g., Ephedra Pine:a typical Gymnosperm Gymno=naked Gymno=naked Sperm=seed Sperm=seed Seed: plant embryo packaged with a food supply within a protective coat Other gymnosperms: Gingko biloba Cycads 4 1/28/2008 A quick survey of vascular plants Angiosperms (flowering plants) Ovary as a protective chamber for developing seeds (fruit) Provide most of our food, fiber, and food fiber livestock forage stamen petal sepal carpel ovule in an ovary Angiosperm flower structure Evolutionary trends in plant reproduction over time Spores (dispersal only; asexual and sexual) Moss Fern Seeds (dispersal with food supply; sexual) Gymnosperms Plants and humans 150 species grown commercially as crops 12 species main source of food World's most nutritious plant Quinoa relative of spinach and beets Extremely nutritious seeds 16% protein, all essential amino acids, iron, calcium, phosphorus, B vitamins Fruit (dispersal with food supply and protection; sexual) Angiosperms Easy to grow; resistant to drought, frost, salty soils Staple of South American diets with corn and potatoes, helped feed Incas Plants and humans Kwashiorkor protein malnutrition prevalent in Peru and Bolivia International programs to select q various strains of quinoa to conserve, improve, and use genetic diversity Maintain nutritional value and cultural preference for seed sizes and colours 5 ...
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